Electrical glow device



March 31. 1925.

G. M. J. MACKAY ELECTRICAL GLOW DEVICE Fi1ed Jan. 26, 1920 InventorALI/AM Mfr/1A UM MM C e a m m o lug/u m fl e%.@

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Patented 31, 1925 enonqn m. J. mcx'air, or scnnnncmnx NEW YonxfAssIeNon'ro GENERAL nine .1310 COMPANY, A CORPORATION OF NEW YORK.

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\ Application filed January 26, 1820. .Seflal No. 354,195.v

To all whom it may concern:

Be it known that I, GEORGE M. J. MAGKAY,

' a citizen of the United States, residing at Schenectady, in the countyof Schenectady, State .of New York, have invented certain new and usefulImprovements in Electrical Glow Devices, of whichthe following is aspecification. 1 v

The present inventionrelates to electrical glow devices and comprises ameans and a method of producing an electrical discharge having new andtechnically useful characteristics. I p

My invention in one of its aspects 'is an electric lamp of higherefficiency than herebefore attainable. Q

I have discovered .that' an electric discharge from an incandescentcathode in thevapor of an alkali metal at pressures below about fiftymicrons of mercury (0.05 mm. Hg.) and preferably within a range of vaporpressure corresponding to' temperatures between about 200 to 300 0.11098not cause the cathode to disintegrate or sputtelnf What is still moreremarkable, the

cathode does not disintegrate even when the Y discharge is operated atvcommercial voltages, that is, over one hundred volts and with relativelylarge currents, say, over 100 milliamperes.

- stable voltsampere characteristic when the applied voltage is withinthis range and the current is relatively large. The currentincreaseswith a rising voltage up to a limiting value, and thereafterremainssubstantially constant over a relatively wideirange of voltage.This discharge has a high luminous efliciency, a large part of theenergy being emitted in the visible portion of the spectrum. It does notrequ re an energyconsuming, steadying resistance, and therefore may beoperated in shunt to an incandescent filament to constitute a lamp of'high efficiency. J E

These and other novel features of my invention will be pointed out withparticularity in the appended claims. For a complete understanding of myinvention, reference may be had to the. following description taken inconnection with the accompanying drawings.

Figs. "1 and 2 illustrate somewhat d ia grammatically two embodiments ofmy, m-

vention; Fig. 3 is a modification having a The discharge hasadouble-walled container to reduce heat dissipat1on,'and Fig. 4 is a diaam of, the volt-ampere characteristics 0 thermionic dischar es-insodiumvapor.

The evice illustrated by Fig.2 comprises material'not readily acteduponchemically by the filling material, for example, the refractorybore-silicate known in the market a'sealed envelope 5 cofisistingofasuitable as Pyrex glass; The cathode 6 consists of a coiled filament ofrefractory material, such, for exatrTple, as tungsten. It is providedwith leading-in conductors 7 8,

sealed into the envelope whereby current may be supplied to the filamentto heat the same to incandescence. The anode 9 consists preferablyof'tungsten although various conductivematerials also may be used.A'leading-in conductor '10 forthe anode is sealed into the envelope inthe usual manner.

In preparing the device, the envelopeis thoroughly exhausted the glassbeing heated during exhaust nearly to its softening point A quantity ofpure to remove water vapor. sodium is introduced into thebulb. afterresidual gases and vapors have been removed, .as far as possible, andthe bulb thereupon is sealed off. Preferably the process of exhaust iscarried out by first introducing a small amount of sodium Into a driedand exhausted bulb, heating the bulb and expelling the sodium vapor.ThlS quantity of purified and redistilled sodium is introduced andallowed to remain in the bulb. The bulb is operated at a temperaturehigh enough tovolatilize' a portlon of" the sodium and maintain thepressure of the sodium vapor high enough to be iomzed by the electrondischarge and within the range throughout which the discharge has stableprocess may be repeated. Finally a desired characteristics. Preferablythe bulb should be maintained within a range ofabout 200 to 300 C. Thistemperature may be 'obtainedby proportioning the bulb so that thedissipation of heat under ordinary external conditions is adjusted to mantam the temperature within the desired range, or the bulb' may beheated or cooled externally to maintain the temperature within thedesired range.

With the cathode at. a suitably high temperature, the application ofcurrent of suitable voltage to the electrodes produces a brilliant glowin the bulb of the yellowish tint characteristic of the sodium spectrum.

'A peculiar characteristic of the glow is of the order of a tenth theuniform distribution of luminescence throughout the bulb which may bedue to optical resonance effects in the sodium vapor. The lighteificiency of the glow appears to be very high. It is approximately of awatt per candle. The presenceof the ionized vapor greatly increases thecurrent-carrying capacity the device by substantial elimination of thecurrent limiting effect of the negative" field i operating of theelectrons on each other which is usually known as space charge. Forexample, a given devicecarrying in the substantial absence of positiveionization about three milliamperes at 125 volts carries in the presenceof sodium vapor at a suitable pressure a current of about 500milliamperes at the same voltage. temperature in these devices shouldcorrespond to a luminous efficiency of about one then remainssubstantially constant with further increase of voltage over a widerange until a second increase of current occurs when the dischargecharacteristic becomes negative, as indi-- cated by the dotted line.From zero to a limiting value of voltage on, the discharge is stablewithout a series resistance, as the current cannot increase without arise of applied voltage. Above the voltage 00. the discharge becomesunstable. An attempt 'to increase the voltage further results in anarc-like or runaway discharge in which the current increases with acorresponding I decrease of voltage across the terminals of thedischarge electrodes.

When the temperature of the device is increased, and hence the pressureof sodium vapor is increased, the critical point of instabilitycorresponds to lower voltage values, that is, the operating ran e of thedevice is contracted. At a su ciently high pressure of sodium vapor,corresponding, y: rent voltage characteristic of the deviceis negativeat ordinary commercial voltage and is similar to the characteristic ofincan- Ordinarily the cathode Asillustrated by this curve the "currentrises rapidy with an increase of voltage from .zero,

to a temperature above 400 C. the our descent cathode devices operatedin other f vapors or gases at relatively considerable pressures.

The device shown in Fig. 2 may be used as a rectifier of alternatingcurrents or as a lamp. v i v .Fig. 1 illustrates a, lamp embodying myinvention containing a looped filament 14 consisting of tungsten, orother suitable refractorymaterial, and supported upon a frameworkcomprising a stem 15 upon which are mountedtwobuttons 16, 17 ,in whichare embedded hooks 18 upon which the filament is supported. The stem 15and.

the hooks 18 consist preferably of a materialv more refractory thanglass, for example, such as tungsten, Nichrome or, the like. The buttons16, 17, in which the hooks 18 are embedded consist either of suitableheatresisting glass or of porcelain. Current connection is made i byconductors 19, 20, consisting of relatively heavy wires composed oftungsten, molybdenum or the like. These wires preferably extend from theseal 21 to the opposite end of the frame-work where'attachment is madeto the ends of the filament in the usual manner.- The lamp is exhaustedand provided ,with a quantity of metallic sodium, as already describedin connection with the device shown in Fig, 2.

When a lamp embodying my invention constructed and prepared as abovedescribed is operated in the usual way on either direct or alternatingcurrent, a discharge will pass through'theisodium vapor acrosstlie spacebetween the loops of the filaments by reason of the difference ofvoltage between these filament sections and cause theentire bulb tobepervaded with a brilliant yellow glow.

The amount of light obtained from a glow ably great and depending uponthe size of the bulb may emit several times the candle power of thefilament. These efl'ects, which are of such a different order from thosehitherto observed with gases at such low pressures, may be partly due tothe purity of the sodium vapor. The sodium vapor itself seems to'bringthis about by cleaning up any traces of foreign gases which may bepresent.

In an alternatingcuri-ent device the conductors immediately adjacent theleading-in wires have alternately the highest positive otential and actas anode for the discharge and 3, the in conduceby preventa .ijacent themin other morenegatiie filament sections. These sections therefore tendto overheat as ing overheating of the same, .The lamp shown in. Fig. 3has a double-walled envelope, the space between the twogwalls Ipreferably being evacuated. This construcby Letters Patent of the UnitedStates, is

1. An electrical discharge device comprising a cathode adapted to beheated to incandescence, heating means therefor, an

anode, and means for furnishing, subject to the ionizing influence of anelectron discharge between-said electrodes, a gas which .when ionizedwill leaveisaid electrodes intact from electrical disintegration, saidgas having a pressure at which a discharge of stable characteristics mabe produced with currents of the order oi magnitude of 100 milliamperesat voltages materially above the ionization voltage of said gas 2. Anelectric discharge device comprising a sealed envelope, means forproducing therein an ,electron discharge and a sublsaae L 6. Anelectrical discharge device comprismg the combination of a tungstencathode, an anode, means for heating said cathode,

an enclosing bulb and aquantity of sodium in said bulb, said lamp beingproportioned to maintain the vapor pressure of said sodium below thevalue at which vthe voltampere characteristic of a'dischargetherecombination of an enclosed envelope, a

cathode adapted to opeate at incandescence, an anode, and a quantity ofsodi'umin said envelope, said envelope being proportioned to operate ata -temperature 'at which the vapor pressure of said sodiumissuificiently high to enable an electric discharge there-- through toionize said vapor but below the value at which a discharge through saidY device has a negative .voltampere characteristic.

8. An electrical device comprising the combination of a sealed envelope,a cathode v of refractory material adapted to operate at incandescence,an anode and 'a quantity of sodium within said envelope, said devicehavinga heat dissipating capacity adapted to maintain-said device at atemperature corresponding to a pressure of sodium vastance within saidenvelope having a prespor less than about fifty microns of mercury.

sure less than about fifty microns of mercury at the operatingtemperature of said device-and capable of becoming ionized in the spacebetween said electrodes to increase materially the currentcarryingcapacity of an electrical discharge betweenan incandescentcathode and an anode through sodium vvapor and maintaining the pressureof said vapor at a value at which a luminous discharge is producedhaving a stable electrical characteristic.

4:. The method of converting electrical en ergy into light whichconsists in passing an electrical discharge through sodium vapor andmaintaining the pressure of saidvapor within the range of vapor pressureof metallic sodium corresponding to temperatures between about 200 to300 C.

5. An electrical device comprising ,the combination of a sealedenvelope, a-refrac- 7 tory cathode adapted to operate at (incandescence,an anode and a quantity of alkali metal within saidenlgelope, saiddevice having a heat dissipating capacity adapted to maintain the vaporpressure of said alkali metal at avalue at which an electrical dischargetherethrough has stable electrical characteristics.

. in said bulbwhich' is gaseous at the operat;

ing temperature of the lamp and is capable ofconducting a luminousdischarge from an end of said filament when at incandescence to theopposite end, and in parallel with the connecting art withoutdisintegrating said filament, said discharge having a constant currentvalue over a range of voltages.

10. An electric lamp comprising a bulb, a conductor therein capable ofconducting current with a voltage drop between termimale of theorder ofmagnitude of about one hundred volts and a quantity of material thereinhaving at the operating tempera-- ture of the bulb a vapor ressuresufiiciently high to conduct current y a stable electricaldischargeacross the space in said'bulb between; a section of saidconductor when at incandescence, and another section havin a positivepotential with respect to' said mcandescent' section. ,g r 11. Anelectric lamp comprising a sealed exhausted container, a quantity ofmetallic sodium in said container, and a filament of heat generatedtherein at a rate which will maintain the operating temperature of saidvlamp at a value at which the pressure of said sodium is high enough toproduce a glow discharge, but below about 300 C. to

avoid the formation of an arc-like discharge 1 a" filament of refractorymaterial therein, a and a uantity of metallic sodium in said bu1b, sa1d.devlcebeing operable with a dis-. charge having a stable electricalcharacteris- I tic conducted through said sodium in a vaporized' state,in parallel with a portion of.

said filament.-, g

- v14. The method of increasing the current-' carrying'capacity of anelectron discharge which consists in maintaining in the path of saiddischarge the vapor of an alkalrmetal within 'ressure limitssufiiciently high to cause su stantial positive ionization by collisionbut insufficient to permit of an arclike discharge having a negativevolt-ampere characteristic. i

15. An electrical discharge device coinpris ing an evacuated envelope,electrodes therein, means for heating one of said electrodes to'incandescence independently of a dis charge therebetween, an alkalimetal contained therein, said device being construct ed to maintain thevapor pressure of alkali -which a discharge througli metal duringoperation high enough to increase the current carrying capacity of saiddevice, but below the value at which an arclike discharge of negativevolt-ampere characteristic may occur.

16. An electrical discharge device comprising a container, cooperatingelectrodes therein, means for producing an electron discharge betweensaid electrodes, a quantity 'of an alkali metal in said container, andmeans surrounding said container for maintaining'the temperature of saiddevice at a value at which the metal vapor has a sufficiently highpressure to' permit. substantial positive ionization during operationbut:

will not be so high astto permit an arc-like discharge. y

17. An electrical discharge'device comprising a sealed evacuatedenvelope, a. filamentarycathode consisting of refractory inate rial,terminal conductors therefor whereby a heating current maybe conveyed tosaid cathode, an anode, I metal in said. envelope, I pro ortioned, whendissipating heat under ordinary external conditions, to operate at atemperature at which the vaporfpresstire of said alkali metal issufliciently high-to enable an electric dischargetherethrough to ionizesaid vapor but below the- 'value at aract'efihtie'ia negativevolt-ampere c o In witness whereof, I have heiieuntoset .my hand this22nd day of January 1920.,

GEORGE M. J KAY and a quantity of alkali said device being said d evicehas

